We propose to examine maternal-infant transfer of cell mediated immunity using both a common virus model, influenza infection in the mouse, and a bacterial model, delayed type hypersensitivity to mycobacterium in the mouse and cow. In the mouse-influenza model, we will selectively suppress influenza specific serum antibody in the mother mouse prior to mating and delivery. Newborn mice of these mothers will be examined for evidence of non-serum-antibody transfer of immunity by assaying for anti-influenza cell-mediated cytotoxicity and by challenging the newborn mice with influenza virus and following virus shedding and mortality. Mice and cows will also be sensitized to heat killed mycobacterium. The infants of these mice and cows will be followed for evidence of delayed type hypersensitivity. If evidence for transfer of cell-mediated immunity is found with any of these three animal models, cross-fostering experiments will be used to determine if immune transfer takes place by breast feeding or by placental transfer. Assuming that breast feeding does transfer cell mediated immunity, as reported in the literature for other systems, the mechanism of this transfer will be studied by feeding components of milk and subsequently assaying for cell-mediated immunity.